Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$161.82	5.538%	$170.7816	$170.78	$170.80	$170.80
Purchase #2	$26.36	5.719%	$27.8675	$27.87	$27.85	$27.90
Purchase #3	$97.49	6.340%	$103.6709	$103.67	$103.65	$103.70
Purchase #4	$100.54	8.479%	$109.0648	$109.06	$109.05	$109.10
Purchase #5	$211.37	4.852%	$221.6257	$221.63	$221.65	$221.60
Purchase #6	$207.57	12.414%	$233.3377	$233.34	$233.35	$233.30
Purchase #7	$166.34	13.559%	$188.894	$188.89	$188.90	$188.90
7 purchase totals =	$971.49		$1,055.2422	$1,055.24	$1,055.25	$1,055.30